热冲压淬火关键工艺参数研究及温度控制系统开发与试验
发布时间:2018-03-22 21:02
本文选题:热冲压 切入点:模具设计 出处:《江苏大学》2017年硕士论文 论文类型:学位论文
【摘要】:超高强钢板热冲压成形技术是目前车企行业在不牺牲安全性能前提下减轻车身重量、实现节能减排的新型技术和重要途径之一,其中的热冲压模内淬火工艺是一个受多因素影响并决定组织转变和制件质量的核心过程,而淬火工装则是保证工艺路线顺利实施的基础。因此,本文以超高强钢B1500HS作为研究对象,立足于理论和实验,重点对热冲压淬火阶段核心工装(热冲压模具)设计、淬火关键工艺参数(保压压强、保压时间和冷却水流速)以及用于淬火冷却的温度自动控制系统开发方面展开了系统的研究。(1)基于传热学理论,推导出了热冲压模具冷却管道直径d和冷却管道中心距模面高度H的理论求解式并应用;同时结合连续淬火热-力耦合模型对设计的模具水道的冷却能力展开了预测分析。研究结果表明:根据预设淬火背景,应用理论求解式得出d为10mm、H为20mm时即可满足使用要求。(2)自主搭建了一套压力可调、温度实时检测的手动淬火实验装置,对热冲压保压压强、保压时间和冷却水流速三个淬火关键工艺参数展开了系统的实验研究,并以淬火后试样力学性能和微观组织作为评价依据,获得了各工艺参数对淬火工艺的影响规律以及最优工艺参数范围。研究结果表明:针对厚度为1.2mm的B1500HS,为达到热冲压件标准,淬火中保压压强应不小于0.5MPa;为提高生产效率,最优保压压强范围应取15MPa以上;初始成形温度为850℃,最佳保压时间为10s;为满足组织转变速率要求,维持连续生产中温度场动态平衡,冷却水流速至少为5L/min。(3)为满足热冲压淬火阶段板料温降速率要求,并针对板料各区域冷却均匀性以及提高冷却系统的自动化和通用性等问题,自主开发了热冲压淬火温度自动控制系统。研究结果表明:该系统能使淬火后制件各区域皆为完全板条状马氏体,且淬火均匀性较好,硬度值达500HV,能够满足热冲压制件使用要求。
[Abstract]:Hot stamping technology for ultra-high strength steel plate is one of the new technologies and important ways to reduce body weight and achieve energy saving and emission reduction in the automotive industry without sacrificing safety performance. The quenching process in the hot stamping die is a core process which is affected by many factors and determines the structure transformation and the quality of the parts, and the quenching equipment is the basis to ensure the smooth implementation of the process route. Based on the theory and experiment, this paper focuses on the design of the core tooling (hot stamping die) during hot stamping and quenching, and the key technological parameters of quenching (pressure keeping), based on the research object of ultra-high strength steel (B1500HS). Based on the theory of heat transfer, a systematic study has been carried out on the development of automatic temperature control system for quenching and cooling. The theoretical formula of diameter d of cooling pipe and height of cooling pipe center from die surface H of hot stamping die is deduced and applied. At the same time, combined with the coupled model of continuous quenching heat and force, the cooling capacity of the designed die waterway is predicted and analyzed. The results show that: according to the preset quenching background, By applying the theoretical solution formula, it can be concluded that when d = 10mm H is 20mm, the manual quenching experiment device with adjustable pressure and real time temperature detection can be set up, which can maintain the pressure of hot stamping. Three key process parameters of quenching, pressure holding time and cooling water flow rate, were studied systematically, and the mechanical properties and microstructure of quenched samples were used as the basis for evaluation. The effects of various process parameters on quenching process and the optimum range of process parameters are obtained. The results show that for B1500HSwith thickness of 1.2mm, in order to meet the standard of hot stamping parts, the holding pressure in quenching should be not less than 0.5MPa, and in order to improve the production efficiency, The optimal pressure keeping pressure range should be above 15MPa, the initial forming temperature is 850 鈩,
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